Frequencies for first 10,000 rows of abruptio variable in natlterr1994 dataset :

   Abruptio |
   placenta |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |         40        0.40        0.40
          2 |      9,937       99.37       99.77
          9 |         23        0.23      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 22 Dec 2015